The present invention relates to guide, diagnostic, and therapeutic catheters for use in medical procedures. In particular, the present invention relates to an improved therapeutic micro-catheter proximal hub and method of manufacture, wherein the hub is molded around the catheter shaft over a shielding sleeve which prevents damage to the catheter shaft while assuring adequate bonding of the hub to the shaft.
The present invention relates to the field of catheterization of lumens within the human body, particularly lumens in the cerebral, peripheral, and heart vasculature. The invention has application to the manufacture and construction of guide, diagnostic, and drug delivery catheters, as well as balloon catheters.
Many medical procedures include the insertion of a catheter into a lumen of a living body. In the performance of such medical procedures, guide catheters and diagnostic catheters are well known for use in catheterization procedures in the vascular system, such as angiography, angioplasty, and other diagnostic or interventional procedures, such as interventional radiology.
One useful therapeutic application of intravascular catheters is the treatment of intracranial aneurysms in the brain. Approximately 25,000 intracranial aneurysms rupture each year in North America. An aneurysm which is likely to rupture, or one which has already ruptured, may be treated by delivering an embolic device or agent to the interior of the aneurysm. The embolic device or agent encourages the formation of a thrombus inside the aneurysm. The formation of a thrombus reduces the probability that an aneurysm will rupture. The formation of a thrombus also reduces the probability that a previously ruptured aneurysm will re-bleed. Thrombus agents which may be used include liquid thrombus agents such as cyanocrylate, and granulated thrombus agents such as polyvinyl alcohol or alcohol. An additional type of thrombus agent which is frequently used is a tiny coil. Any of the thrombus agents described above may be delivered using an intravascular catheter.
When treating an aneurysm with the aid of an intravascular catheter, the catheter tip is typically positioned proximate the aneurysm site. The thrombus agent is then urged through the lumen of the intravascular catheter and introduced into the aneurysm. Shortly after the thrombus agent is placed in the aneurysm, a thrombus forms in the aneurysm and is shortly thereafter complemented with a collagenous material which significantly lessens the potential for aneurysm rupture. It is desirable that the lumen of the catheter provides a path for delivering embolic devices to an aneurysm. To this end, it is desirable that the pathway through the catheter have a low friction surface.
In other portions of the human body, diagnostic catheters are used for procedures including dye delivery, arterial flushing or arterial pressure monitoring. Diagnostic catheters are also used during cardiac catheterization for diagnosis of coronary artery disease, for defining vessel anatomy, for isolating lesions, and for identifying adjacent cardiac branches which may impinge on a lesion and affect ventricular function. For procedures within the coronary artery, the distal end of the diagnostic catheter is inserted percutaneously into the vascular system of the patient and pushed distally up and over the aortic arch. A proximal end of the catheter protrudes outside of the patient""s body and may be used for implementation of diagnostic procedures, such as dye delivery, flushing, and arterial pressure monitoring.
Angioplasty procedures have gained wide acceptance as an efficient and effective method for treating certain types of vascular diseases. In particular, angioplasty is widely used for stenoses in the coronary arteries, although it is also used for the treatment of stenoses in other parts of the vascular system. The most widely used form of angioplasty makes use of a dilatation balloon catheter to treat a stenosis and thereby reestablish an acceptable blood flow through the artery. The dilatation catheter includes an elongated tubular shaft and an inflatable balloon carried at a distal end of the shaft. In operation, the catheter is inserted through a guide catheter which has been previously introduced into a patient""s vascular system from a location remote from the heart (e.g., femoral artery). The proximal end of the guide catheter remains outside the patient while the distal end of the guide catheter is positioned at the coronary artery ostium. A dilatation catheter is introduced into the proximal end of the guiding catheter and advanced to the distal end of the guide catheter. Then, by using fluoroscopy, the physician guides the dilatation catheter the remaining distance through the vascular system until the balloon is positioned across the stenosis.
In each of the above applications, the catheter commonly includes a hub and/or manifold at its proximal end, which permits the catheter to be more easily handled, and which may incorporate a luer fitting or other connection device which may be attached to an appliance conveying a fluid media or substance which is to be delivered to the distal end of the catheter. In some known catheters, hubs are adhesively bonded to the catheter shaft, while in other known designs, hubs are injection or insert molded onto the catheter shafts. With the insert molding process, the injected molten plastic hub material, because of its high temperature, may be capable of damaging the shaft of the catheter by melting or otherwise deforming it. This may compromise the integrity of the lumen walls in the affected region which may lead to collapse by kinking or other deformation that reduces the lumen diameter.
Under prior methods of injection or insert molding hubs onto catheter shafts, the catheter shaft was afforded protection from the high temperatures of the injected hub material by protective layers placed over the catheter shafts. For example, the catheter shaft might be protected by multiple layers of polymeric films over the catheter shaft in the region of hub attachment. In order to ensure good adhesion of the catheter hub to the shaft, these multiple protective layers require separate lamination of each layer to the shaft and to each other. Accordingly, these prior methods of securing hubs to catheter shafts had a number of drawbacks. The preparation of the catheter shaft prior to hub molding increased the complexity of catheter manufacture, and the increased preparatory steps afforded increased chances for error, quality variations, and rejected products and waste, in addition to increased time and cost of manufacture.
It is desirable to have a plastic molded hub, and a manufacturing process for these hubs, which is less labor intensive than prior methods of producing such catheters with hubs, and which would have reduced defect and scrap rates relative to present techniques of securing the hub to the catheter shaft.
The present invention pertains to a process for the production of intralumenal catheters with an insert molded hub, that does not require extensive preparation of the catheter shaft prior to molding. One embodiment of the present invention provides for a tubular sleeve of material that is compatible with the hub molding media. The tubular sleeve shields the catheter shaft from heat generated during the injection molding process, but transfers enough heat for bonding the sleeve to the catheter shaft. The compatible material of the tubular sleeve thermally bonds with the shaft on the sleeve""s inner diameter, and bonds with the hub molding media on the sleeve""s outer diameter during the single injection molding step. The present invention overcomes disadvantages of previously existing methods for securing the hub to the catheter shaft, and accomplishes hub molding with fewer errors in manufacture. The present invention therefore increases the reliability of the production process, in addition to making the hub to catheter shaft transition seamless, i.e., without weld lines, and therefore more securely affixed to the catheter shaft and less prone to failure or bursting. In addition, fewer additional materials are introduced into production of the catheter.
One embodiment of the present invention is a catheter with a flexible, elongate tubular shaft. This shaft has a lumen therethrough, and has a proximal and a distal end. The catheter shaft may be of any length required to reach the site of therapeutic or diagnostic activity within the patient vasculature, and may also incorporate various therapeutic or diagnostic devices or means at the distal end of the catheter shaft, including an expandable balloon, for example. A hub with an inner lumen is attached to the proximal end of the shaft. A thin polymeric sleeve covers the proximal end of the catheter shaft, and may extend slightly beyond the proximal end of the catheter shaft.
This polymeric sleeve is preferably heat fused to the catheter shaft, and is covered over most of its length by the molded hub of the catheter. Generally, the tubular sleeve must extend over any part of the catheter shaft that will be contacted by the hot melt injection during hub molding.
In a preferred embodiment, the hub injectate material is a polymer such as polyamide, nylon, polyether block amide (PEBA), or mixtures and copolymers thereof. A preferred commercially available suitable material is Grilamid(copyright) TR55LX produced by EMS-Chemie Holding AG/American Grilon, Inc. of Sumter, S.C. Also in a preferred embodiment, the protective sleeve placed over the catheter shaft is made from the identical material. Generally, however, any compatible material for the sleeve will support the subject invention. By a compatible material, it is meant that the sleeve material will form a thermal bond to the shaft, and will also bond to the hot injectate during the molding process. In preferred embodiments, the injectate provides sufficient heat to form the sleeve bond to the shaft by conduction therethrough. Further, in preferred embodiments, the sleeve and injectate material are both clear or optically clear to form a unitary clear hub.
Under a preferred embodiment of the subject invention utilizing a Grilamid(copyright) polymeric sleeve and injectate, where the catheter shaft is made with an inner layer of a fluoropolymer or thermoplastic, and an outer layer of a thermoplastic such as a polyether block amide (PEBA), the polymeric sleeve will have a wall thickness within a range of approximately 0.005 inches to 0.020 inches, while the injectate hub hot media will be heated and injected at a temperature of approximately 450xc2x0 F. to 550xc2x0 F. Following the injection, the hot media is preferably cooled by conduction via a recirculating coolant. Regardless of the polymeric material used to practice or produce the subject invention, the parameters must be regulated so as to ensure an effective heat bond between the inner diameter of the polymeric sleeve and the outer wall of the catheter shaft, but without permitting excessive heat to be conveyed to the catheter shaft so as to permit damage to the shaft.
Another embodiment of the present invention incorporates a flexible strain relief sheathing, surrounding the catheter shaft distal to the area of the hub, but in close proximity to the hub, to prevent crimping and to help prevent a degree of bending that may damage the shaft in the area where it meets the hub. The strain relief is flexible, but not as flexible as the shaft in the area distal to the hub. In a preferred embodiment, the flexible strain relief becomes more difficult to flex as it is flexed, and becomes very difficult to flex as it approaches a degree of flexion wherein the shaft surrounded by the strain relief is near its limit of flexion, i.e., at a point where it is in danger of kinking or folding.
In preferred embodiments, the flexible strain relief is added to the hub after molding and curing of the hub is complete. The strain relief may be made from a polymeric material different than that from which the hub is made. In an alternative embodiment of the present invention, an integral strain relief that is molded as part of, or as an extension of, the hub itself may be utilized. An integrated hub and strain relief is disclosed in commonly assigned pending U.S. patent application Ser. No. 08/971,456, filed Nov. 17, 1997, entitled xe2x80x9cIntegral Hub and Strain Relief,xe2x80x9d the disclosure of which is hereby incorporated by reference.
In this embodiment of the subject invention, the polymeric sleeve placed around the catheter shaft will naturally be longer, because the material that is to adhere to the catheter shaft, i.e., the hub and strain relief integrated structure, is longer than the hub structure alone. Because the strain relief, when injection molded, will be at a temperature that may damage the catheter shaft, the polymeric sleeve must be extended to protect the catheter shaft from this additional molded member. When the strain relief member is integrated with the hub, the polymeric sleeve is used to adhere the integral molded hub and strain relief structure to the catheter shaft, in the same way that the sleeve is used to bond the hub to the shaft in the embodiments of the invention previously discussed.
The present invention further includes a method for manufacturing the hub, and the attendant attachment of the sleeve and hub to the catheter shaft. With this method, the proximal end of the catheter shaft is placed over a pin in a molding core. Thereafter, a polymeric tubular sleeve is placed over the catheter shaft, and is slid down the catheter shaft to the proximal end. In a preferred embodiment, the polymeric sleeve may extend just beyond the proximal tip of the catheter shaft, or may be flush with the proximal tip. Similarly, the distal end of the polymeric sleeve may be flush with the distal end of the catheter hub as defined by the mold, or, in a preferred embodiment, may extend slightly distally of the distal end of the catheter hub. Thereafter, the polymeric material of the catheter hub is injected into the molding core or cavity in which the catheter shaft has been placed. In a preferred embodiment of the subject invention, the heat of the molten hub material imparts sufficient heat to the polymeric sleeve to fuse the polymeric sleeve to the catheter shaft, and to fuse the polymeric sleeve with the hub itself into one unified member; however, the polymeric sleeve is sufficiently thick so that the heat from the molten hub material does not melt or otherwise deform or damage the catheter shaft.